First island species of Hyalella (Amphipoda, Hyalellidae) from Florianpolis, state of Santa Catarina, Southern Brazil.

The Hyalella comprises a group of freshwater amphipods endemic to the Americas. In Brazil, the greatest diversity of species known so far is concentrated in the state of Rio Grande do Sul, but recently discoveries were made in the neighboring state of Santa Catarina. The present work describes the first island species of the genus Hyalella in Brazil and the fifth with occurrence in the state of Santa Catarina. The species was found in streams of two watersheds, located at the Monumento Natural Municipal da Lagoa do Peri, an important environmental protection area on the island of Florianpolis, Southern Brazil. Hyalella insulae n. sp. shows the following characters: inner face of propodus of gnathopod 1 with 7 serrate setae, gnathopod 2 with propodus ovate, peduncle of uropod 3 with 10 cuspidate setae, telson rectangular, wider than long, with 6 cuspidate setae and 2 plumose setae laterally close to each distal seta. H. insulae n. sp. differs from the other species with occurrence in Santa Catarina, H. catarinensis, H. rioantensis, H. sambaqui and H. lagoana, mostly concerning to the number and shape of setae of the gnathopods, uropods and telson. A comparison was also made with species from the neighboring states, Rio Grande do Sul and Paran. The description of H. insulae n. sp. in the present study contributes to increasing the knowledge of the Hyalella diversity in the state of Santa Catarina, little known so far.

The riverine bioreactor: An integrative perspective on biological decomposition of organic matter across riverine habitats.

Riverine ecosystems can be conceptualized as 'bioreactors' (the riverine bioreactor) which retain and decompose a wide range of organic substrates. The metabolic performance of the riverine bioreactor is linked to their community structure, the efficiency of energy transfer along food chains, and complex interactions among biotic and abiotic environmental factors. However, our understanding of the mechanistic functioning and capacity of the riverine bioreactor remains limited. We review the state of knowledge and outline major gaps in the understanding of biotic drivers of organic matter decomposition processes that occur in riverine ecosystems, across habitats, temporal dimensions, and latitudes influenced by climate change. We propose a novel, integrative analytical perspective to assess and predict decomposition processes in riverine ecosystems. We then use this model to analyse data to demonstrate that the size-spectra of a community can be used to predict decomposition rates by analysing an illustrative dataset. This modelling methodology allows comparison of the riverine bioreactor's performance across habitats and at a global scale. Our integrative analytical approach can be applied to advance understanding of the functioning and efficiency of the riverine bioreactor as hotspots of metabolic activity. Application of insights gained from such analyses could inform the development of strategies that promote the functioning of the riverine bioreactor across global ecosystems.